I have found that the following water parameters listed below work best for reef aquariums.
Corals use calcium to form their skeletons, which are composed primarily of calcium carbonate. Corals get the calcium for this process from the water surrounding them.
Calcium – 380-450 ppm
Corals also use “alkalinity” to form their skeletons, which they compose primarily of calcium carbonate.
Alkalinity – 7-11 dKH
There is little evidence that keeping a coral reef aquarium at anything other than natural levels is preferable. However, it’s common practice to keep marine fish, and reef aquaria, at somewhat lower than natural salinity levels.
Salinity – 35 ppt or 1.026
The greatest variety of corals are found in water whose average temperature is about 83-86° F. Therefore, corals do better at the higher temperatures.
Temperature 75-86° F
The pH of natural seawater is about 8.2. Therefore, 8.1-8.3 is appropriate.
pH – 8.1 – 8.3
Magnesium has an important interaction with the calcium and alkalinity balance in reef aquaria.
Magnesium – 1250 – 1350 ppm
Phosphate causes algae growth. Therefore, elevated phosphate levels are problematic.
Phosphate – < 0.03 pp
Ammonia (NH3) excreted by animals and other aquarium inhabitants is very toxic to all animals.
Ammonia – < .1